Sunday, August 7, 2011

Aero mass-start frames and the Tour de France

The trend continues that the big bike companies (manufacturers isn't quite the term, since so few of them actually manufacture anything... perhaps "branders" is a better term...) are delivering aerodynamically optimized road frames designed for use in mass-start road races. These bikes go way back, at least as far back as the Kestrel Talon. But the use of the bikes at the top pro level really began with the Cervelo Soloist (Bobby Julich won Paris-Nice on the bike). Then the Cervelo SLC and SLC-SL really got things rolling. Then Ridley came out with the Noah and Felt with the AR, and Fuji with the SST. And these are just the bikes of top-level pro teams. Kestrel updated the Talon (and Talon-SL), and Litespeed came out with its stunning Archon-CF; neither of these bikes got pro-level attention, however (Kestrel briefly sponsored third-tier Rock Racing, but Rock used their stiffer RT-800).

Yet except for the Cervelo, all of these frames seemed to encounter resistance from riders on the teams using the brands. What was up? The frames were heavier, typically around 250-300 grams heavier than a frame designed without consideration for aerodynamics other than fork shaping, but with the UCI mass limit at a relatively beefy 6.8 kg, with carbon-rimmed wheels there's still plenty of room for heavy frames for bike at the rule-limited mass. And even with Cervelo, many of the riders chose the R3 (or R3-SL) over the SLC-SL, despite Cervelo super-engineer Gerard Vroomen's claims the SLC-SL was the far faster bike on virtually all terrain, even without a weight limit to equalize mass. The epitome of this was the 2008 Tour de France, where team leader Carlos Sastre flaunted the wind tunnel by riding the R3. He then won the yellow jersey.

The issue, obviously, was the feel of the bikes. Aero frames have a reputation for a poor trade-off between ride quality and stiffness. The Kestrels have a reputation for smooth ride, but poor stiffness. On the other side, the Ridley was said to be super-stiff, but an uncomfortable ride.

In the 2008 Olympics Cervelo released the S-series, with the pro-level frame being the S3. Now even more of the riders on Cervelo-sponsored teams were using this over the R-bike. It was the first aero-optimized frame to get relatively wide acceptance among pro riders.

But this was just the start. Scott revealed the F1 (later called Foil) at the 2010 Tour. The entire HTC-High Road team road the bike, with the exception of Mark Cavendish who switched back to his customized (extra beef) Addict bike after the first few stages. After the switch, Mark went on to win five of the final 15 mass-start stages.

But this year saw some of the biggest brands in cycling deliver the goods. First Specialized debuted the Venge at Milan San Remo, and the bike promptly won that epic classic with a rider, Matt Goss, who wasn't a favorite. All about the bike, right? Then Cervelo came out with the impressive R5, which looks a lot like a Felt AR but with a skinnier head tube.

Cervelo S5 from its most flattering view

Both frames showed impressive success in the Tour this year. Mark Cavendish rode his Venge to five stage wins, while Thor Hoshovd rode his S5 to two stage wins and a remarkable seven-day run in the yellow jersey (he started the Tour on an S3, but switched to a yellow S5 when he got the jersey). Hoshovd's reign seemed to validate Vroomen's claim of the benefits of aerodynamics on hilly terrain, as he against hope managed to twice cling onto lead groups of GC favorites to defend his GC lead against eventual winner Cadel Evans by just a few seconds.

So it seems the revolution was finally being won by the aero frames. After years of wind tunnel data showing that only a fool would take a round-tube bike into anything more competitive than a friendly bike commute, the pros were finally coming to their senses and the aero road frames were rising to a position of permanent dominance.

So when the dust had settled on the final sprint into Paris, how did they do in the final GC? In the Tour, top 20 is generally considered a noteworthy result: below that and a large number of the riders were burdened with other priorities, like team duties or focusing on stage wins, so actual placing is far less meaningful. So I'll focus on top 20. How many of the top 20 were on aero-optimized frames? Here's the result (from CyclingNews):

The answer: none of the top 20 riders were on aero-optimized road frames (reference). Sure, the Garmin-Cervelo riders had the option of the S3 or S5, but Tom Danielson, Ryder Hesjdal, and Christian Vande Velde were all on R5's. And taking these riders as the prime contributors to their team's win in the team general classification, none of the top 3 teams in GC got there aero road frames. The team GC podium teams, Leopard-Trek and Europcar (on Colnagos) were on round-tube frames.

So what do you conclude from this? Two choices:
1. The fools! Every one of the top twenty would have been even faster had they seen the light of science and ridden aerodynamically optimized bikes. Wind tunnel data do not lie!
2. There's a lot more to bike racing than wind tunnel data.

It's remarkable, really. Every single test shows these bikes a substantial (on order 5%) reduction in wind drag from riding an aerodynamically optimized frame. Even if this is less important during crunch time on the climbs, the advantage, even while drafting, should be enough that it leaves riders fresher to deliver power during these critical periods. But the results simple don't show it.

Word is Cannondale and Trek will both enter the game soon. Maybe the aero-optimized frames will finally show their advantage. Or maybe the advantage is less than simple analysis suggests.

4 comments:

From his own blog today http://gerard.cc/2011/08/08/body-position-vs-bar-height-part-3/

"Of course, that said no pro should ever ride the R3 except for Paris-roubaix (which it was designed for originally). The aero frames are ALWAYS the fastest solution, even in mountainous terrain, so every pro taking their profession seriously and wanting to get to the finish the fastest should ride them at all times (except Roubaix)."

My own personal take on this is that it is worth riding an aero-frame... marginal gains and all that. But ONLY if in the process of doing so one does not reduce or compromise power output or increase fatigue.

As you say it is more complicated than putting a frame on a jig in a wind tunnel and simply measuring drag.

I love Gerard's blog. Cervelo was the one that did "Col de la Tipping Point" years ago deminstrating the SLC should be faster than the R3 in anything except a steep uphill time trial... if you look at the numbers, the round tube bikes should simply be non-competitive. So your take seems spot-on. How do you quantify fatigue and comfort or, for that matter, stiffness? If you feel more confident on a bike, and can move up ten spots in the peloton by the base of a climb, that's a huge advantage which won't show up in any power-speed equation.

I can attest to the Noah being super, super stiff. One can feel the stiffness of the front end in cornering and braking, and it's rock solid when putting down the power in a sprint.

I'm not a pro stage racer, so even a 5 hour ride for me with off road bits is tolerable on the bike. I could see how day after day of 5 hour races it might feel fatiguing.

It sure handles better than any other bike I've ridden, very fast and responsive.

Without spending significant time and effort doing testing, I can't say if it's aerodynamically faster or not. But the rigid feel and handling alone make it a superior crit/race type bike over anything else I've ridden.

As I'm racing less though, I keep thinking about a bike that might be a little more comfortable and forgiving when I wonder off road or onto rough surfaces.